alignerr: what does "offline access" mean?

I tried signing in on alignerr for the first time using my google account. The first screen I get is a request saying:

Alignerr is requesting access to your alignerr account.

• Profile: access to your profile and email
• Allow offline access

Does anyone know what "offline access" mean here? My home internet provider's security service thinks this is a "security threat" and immediately blocked it. I am little skeptical about accepting the request. Can anyone who has used their service before know if it is safe to go ahead? Am I seeing something which wasn't there earlier? It might seem that I just clicked on some illegitimate link, but this is what I see when I directly go from their main page.